Method of converting feedstocks from renewable sources to good-quality diesel fuel bases using a zeolite catalyst without intermediate gas-liquid separation

ABSTRACT

The invention relates to a method of treating feedstocks from renewable sources without intermediate gas-liquid separation in order to produce diesel fuel bases of excellent quality. The feedstocks used can be raw vegetable oils or such oils that have been previously subjected to a prerefining stage, animal fats, or mixtures of such feedstocks. The invention relates to a method allowing high diesel fuel base yields to be obtained from such feedstocks.

FIELD OF THE INVENTION

In an international context characterized by the fast growth of fuelneeds, in particular diesel fuel bases in the European community, thesearch for new renewable energy sources that can be integrated in theconventional refining and fuel production scheme has become a majorchallenge.

Integration, in the refining process, of new products of vegetableorigin, resulting from the conversion of lignocellulosic biomass or fromthe production of vegetable oils or animal fats, has therefore knownrenewed interest in the last few years because of the increase in thecost of fossil materials. Similarly, conventional biofuels (mainlyethanol or vegetable oil methyl esters) have acquired a real status as acomplement to petroleum type fuels in gasoline pools. Besides, theprocesses known to date using vegetable oils or animal fats are thecause of CO₂ emissions known for their negative effects on theenvironment. A better use of these bioresources such as, for example,their integration in the gasoline pool, would therefore be an undoubtedadvantage.

The great demand for diesel fuels, combined with the high concern forthe environment, reinforces the interest of using feedstocks coming fromrenewable sources. Examples of such feedstocks are vegetable oils,animal fats, raw or subjected to a preliminary treatment, as well asmixtures of such feedstocks. These feedstocks contain chemicalstructures of triglyceride or ester or fatty acid type, the hydrocarbonchain structure and length of the latter being compatible with thehydrocarbons present in diesel fuels.

A possible approach consists in converting the vegetable oil typefeedstocks by transesterification. The triglycerides that essentiallymake up such feedstocks are then converted, in the presence of analcohol and of a catalyst, to corresponding esters. The followingdrawbacks of this approach can be mentioned: a) the increase in NOxemissions, due to the presence of oxygen in the esters; b) the ratherhigh boiling-point temperature, of the order of 360° C., which may poseproblems for meeting the end point specifications.

BACKGROUND OF THE INVENTION

Patent application No. EP-1,681,337 A describes the conversion offeedstocks from renewable sources by decarboxylation in order to producemiddle distillates. The advantage of this option consists in limitingthe necessary hydrogen consumption. The method comprises an optionalpretreatment stage followed by an isomerization stage using a catalystcontaining a molecular sieve selected from among SAPO-11, SAPO-41,ZSM-22, ferrierite or ZSM-23 and a group VIII metal selected from amongpalladium, platinum and nickel, said method operating at a temperatureranging between 200° C. and 500° C., and at a pressure ranging between 2and 15 MPa, the catalysts used being metallic catalysts. The diesel fuelbase yields obtained with this method are however not maximized.

U.S. Pat. No. 4,992,605 describes a method of producing diesel fuel poolbases produced from the direct conversion of vegetable oils (rape, palm,soybean, sunflower) or lignocellulosic biomass to saturated hydrocarbonsafter hydrotreatment or hydrorefining of these products in the presenceof a catalyst based on cobalt and molybdenum, at a temperature rangingbetween 350° C. and 450° C. and at a pressure ranging between about 4.8MPa and 15.2 MPa. These conditions allow to obtain products with a highcetane number. The pro-cetane additives thus obtained are mixed with thediesel fuel in proportions ranging from 5 to 30% by volume. However,this method has the major drawback of involving a high hydrogenconsumption due to the methanization or water-gas shift reactions.Besides, the oxygen contained in the triglycerides is generallydecomposed by hydrodeoxygenation in the presence of a hydrotreatingcatalyst, which is costly in oxygen.

Patent application EP-1,741,768 describes a method comprising ahydrotreatment stage, followed by a hydroisomerization stage in order toimprove the cold properties of the linear paraffins obtained, anintermediate stripping stage being preferably carried out. The catalystsused in the hydroisomerization stage are bifunctional catalystsconsisting of a metallic active phase comprising a group VIII metalselected from among palladium, platinum and nickel, dispersed on amolecular sieve type acidic support selected from among SAPO-11,SAPO-41, ZSM-22, ferrierite or ZSM-23, said method operating at atemperature ranging between 200° C. and 500° C., and at a pressureranging between 2 and 15 MPa. However, using this type of solid leads toa middle distillate yield loss for diesel fuel production.

One advantage of the invention is to provide a method allowing, fromfeedstocks coming from renewable sources, to obtain high diesel fuelbase yields while allowing reduced hydrogen consumption.

OBJECT OF THE INVENTION

The present invention relates to a continuous method of convertingfeedstocks coming from renewable sources to diesel fuel bases.

The initial feedstocks come from renewable sources such as oils and fatsof vegetable or animal origin, or mixtures of such feedstocks,containing triglycerides and/or fatty acids and/or esters. Possiblevegetable oils, which can be raw or refined, totally or partly, can comefrom the following vegetables: rape, sunflower, soybean, palm, palm-nut,olive, coconut, jatropha, but this list is not limitative. Algae or fishoils are also pertinent. Examples of possible fats are all the animalfats such as lard or the fats consisting of food industry residues orfrom the catering industries.

The feedstocks thus defined contain triglyceride and/or fatty acidstructures whose fatty chains contain a number of carbon atoms rangingbetween 8 and 25.

The hydrocarbons produced upon conversion of the initial feedstocksaccording to the invention are characterized by:

a) a number of carbon atoms equal to that of the initial fatty acidchains, if the mechanism is a mechanism of hydrogenation of the carboxylgroup to an alkyl group,

b) a hydrocarbon chain comprising one carbon atom less than the initialfatty acid chains, if the mechanism involved isdecarboxylation/decarbonylation,

c) an adjusted hydrocarbon branching degree so as to obtain coldstrength properties and a cetane number compatible with the currentstandards for diesel fuel.

It is well known from the state of the art that conversion options a)and b) generally co-exist. The method described in the present inventionconsequently aims to maximize the diesel fuel yield and to promote thehydrogenation mechanism described in a). Selection of the catalysts andof the operating conditions thus tends to orient the selectivity infavour of hydrogenation, while trying to limit to the bare essentialsthe hydrogen consumption, in particular one that would result in theappearance of unwanted reactions. Besides, the method described in thepresent invention also aims to substantially isomerize the paraffins ofthe diesel fuel cut while limiting their cracking to unwanted lighterfractions such as, for example, the naphtha cut.

The diesel fuel bases produced are of excellent quality:

-   -   they have a low sulfur, nitrogen and aromatics content,    -   an excellent cetane number due to the substantially paraffinic        structure of the hydrocarbons formed,    -   good cold strength properties due to the degree of isomerization        of the paraffins of the cut,

a low density (generally less than 800 kg/m³), which is an advantageinsofar as the specification for the diesel fuel pool that is 845 kg/m³maximum is more easily obtained.

One objective of the invention is to provide a method of treating afeedstock from a renewable source comprising a hydrotreatment stage,followed by a water separation stage and a stage of removal of thenitrogen compounds from the hydrocarbon base obtained, prior tohydroisomerization of said hydrocarbon base, i.e. ahydrotreatment/hydroisomerization sequence without an intermediategas-liquid separation stage.

Another objective of the invention is to allow, by carrying out, betweena hydrotreatment and hydroisomerization stage, successively, a waterremoval stage and a nitrogen compound removal stage, without anintermediate gas-liquid separation stage, treatment of the hydrotreatedeffluent that has not been freed of sulfur-containing contaminants suchas H₂S.

An additional objective of the invention is to carry out thehydroisomerization stage in the presence of sulfur compounds that havenot been removed after the hydrotreatment stage in the presence of aparticular thioresistant catalyst.

One advantage of the invention thus is to use a combination of ahydrotreatment stage a) operating under precise operating conditionsallowing reduced hydrogen consumption and of a hydroisomerization stageusing a particular hydroisomerization catalyst, without intermediategas-liquid separation, allowing both to treat a hydrotreated effluentcomprising sulfur-containing contaminants and to obtain a high dieselfuel base yield, as well as reduced H₂ consumption.

SUMMARY OF THE INVENTION

The invention relates to a method of treating a feedstock from arenewable source, comprising the following stages:

a) hydrotreatment in the presence of a fixed-bed catalyst, said catalystcomprising a hydro-dehydrogenizing function and an amorphous support, ata temperature ranging between 200° C. and 450° C., at a pressure rangingbetween 1 MPa and 10 MPa, at an hourly space velocity ranging between0.1 h⁻¹ and 10 h⁻¹ and in the presence of a total amount of hydrogenmixed with the feedstock such that the hydrogen/feedstock ratio rangesbetween 150 and 750 Nm³ hydrogen/m³ feedstock,

b) separation, from the effluent from stage a), of at least part of thewater and at least one hydrocarbon-containing base,

c) removal of the nitrogen compounds from said hydrocarbon-containingbase from stage b),

d) hydroisomerization of at least part of said hydrocarbon-containingbase from stage c) in the presence of a fixed-bed hydroisomerizationselective catalyst, said catalyst comprising at least one group VIIImetal and/or at least one VIB group metal and at least onemonodimensional 10 MR zeolite molecular sieve, said stage c) beingcarried out at a temperature ranging between 150° C. and 500° C., at apressure ranging between 1 MPa and 10 MPa, at an hourly space velocityranging between 0.1 h⁻¹ and 10 h⁻¹ and in the presence of a total amountof hydrogen mixed with the feedstock such that the hydrogen/feedstockratio ranges between 70 and 1000 Nm³/m³ feedstock,

e) separation, from the effluent from stage d), of the hydrogen, thegases and at least one diesel fuel base.

DETAILED DESCRIPTION

The present invention is particularly dedicated to the preparation ofdiesel fuel bases corresponding to the new environmental standards, fromfeedstocks coming from renewable sources.

These feedstocks consist of all of the vegetable oils and animal fats,essentially containing triglycerides and fatty acids or esters, withhydrocarbon fatty chains having a number of carbon atoms ranging between6 and 25. These oils can be palm, palm-nut, copra, castor and cottonoil, peanut, linseed, crambe and jatropha oil, all the oils resultingfor example from sunflower or rapeseed through genetic modification orhybridization, as well as algae oils. Waste kitchen oil, various animaloils such as fish oil, tallow, lard can also be used.

The densities at 15° C. of these oils range between 850 and 970 kg/m³and their kinematic viscosities at 40° C. range between 20 and 400mm²/s, more generally between 30 and 50 mm²/s.

These feedstocks are free of or have low sulfur, nitrogen and aromaticscontents: sulfur and nitrogen contents typically below 500 ppm andaromatics contents below 5% by weight.

Advantageously, the feedstock can be subjected, prior to stage a) of themethod according to the invention, to a pretreatment or prerefiningstage so as to remove, by means of a suitable treatment, contaminantssuch as metals, alkaline compounds for example on ion-exchange resins,alkaline-earth metals and phosphorus. Suitable treatments can forexample be thermal and/or chemical treatments known to the personskilled in the art.

The optional pretreatment preferably consists in a mild prehydrogenationof said feedstock so as to avoid secondary reactions of the doublebonds. Mild prehydrogenation is advantageously operated at a temperatureranging between 50° C. and 400° C., at a hydrogen pressure rangingbetween 0.1 and 10 MPa and preferably at a temperature ranging between150° C. and 200° C. The prehydrogenation catalyst advantageouslycomprises group VIII and/or VIB metals and, preferably, theprehydrogenation catalyst is a catalyst based on palladium, platinum andnickel, nickel and molybdenum or based on cobalt and molybdenum,supported by an alumina and/or silica support.

The metals of the catalysts used in the optional pretreatment stage ofthe method according to the invention are sulfur-containing metals ormetallic phases, preferably metallic phases.

Stage a): Hydrotreatment of the Feedstock from a Renewable Source

In stage a) of the method according to the invention, the feedstock,possibly pretreated, is contacted with a heterogeneous catalyst at atemperature ranging between 200° C. and 450° C., preferably between 220°C. and 350° C., more preferably between 220° C. and 320° C. and mostpreferably between 220° C. and 310° C. The pressure ranges between 1 MPaand 10 MPa, preferably between 1 MPa and 6 MPa, and more preferablybetween 1 MPa and 4 MPa. The hourly space velocity ranges between 0.1h⁻¹ and 10 h⁻¹. The feedstock is contacted with the catalyst in thepresence of hydrogen. The total amount of hydrogen mixed with thefeedstock is such that the hydrogen/feedstock ratio ranges between 150and 750 Nm³ hydrogen/m³ feedstock, preferably between 150 and 700 Nm³hydrogen/m³ feedstock, more preferably between 150 and 650 Nm³hydrogen/m³ feedstock and most preferably between 150 and 600 Nm³hydrogen/m³ feedstock, which thus corresponds to an amount of hydrogenadded to the feedstock present of at least generally 0.5% by weight ofhydrogen in relation to the feedstock.

The amount of hydrogen actually used corresponds at least to thestoichiometric amount required for complete hydrogenation of thefeedstock to paraffin. It therefore depends on the nature of thefeedstock.

In stage a) of the method according to the invention, at least one fixedhydrotreatment catalyst bed comprising a hydro-dehydrogenizing functionand a support is used. A catalyst whose support is for example selectedfrom the group made up of alumina, silica, silica-aluminas, magnesia,clays and mixtures of at least two of these minerals is preferably used.This support can also contain other compounds and, for example, oxidesselected from the group made up of boron oxide, zirconia, titaniumoxide, phosphoric anhydride. A support consisting of alumina, morepreferably of η, δ or γ alumina is preferably used.

Said hydrogenizing function of the catalyst used in stage a) of themethod according to the invention is advantageously provided by at leastone group VIII and/or group VIB metal.

Said catalyst can advantageously be a catalyst comprising group VIIImetals such as, for example, nickel and/or cobalt, most often associatedwith at least one group VIB metal, for example molybdenum and/ortungsten. It is for example possible to use a catalyst comprising 0.5 to10% by weight of nickel oxide (NiO), preferably 1 to 5% by weight ofnickel oxide, and 1 to 30% by weight of molybdenum oxide (MoO₃),preferably 5 to 25% by weight of molybdenum oxide on an amorphousmineral support, the percentages being expressed in % by weight inrelation to the total mass of catalyst.

The total proportion of oxides of group VIB and VIII metals in thecatalyst used in stage a) advantageously ranges between 5 and 40% byweight and preferably between 6 and 30% by weight in relation to thetotal mass of catalyst.

The weight ratio expressed in metallic oxide between group VIB metal(s)and group VIII metal(s) advantageously ranges between 20 and 1,preferably between 10 and 2.

Said catalyst used in stage a) of the method according to the inventionhas to be advantageously characterized by a high hydrogenizing power soas to orient as much as possible the reaction selectivity towards ahydrogenation keeping the number of carbon atoms of the fatty chains, inorder to maximize the yield in hydrocarbons falling within thedistillation range of diesel fuels. This is the reason why a relativelylow temperature is preferably used. Maximizing the hydrogenizingfunction also allows to limit the polymerization and/or condensationreactions leading to the formation of coke that would degrade thecatalytic performance stability. A Ni or NiMo type catalyst ispreferably used.

Said catalyst used in hydrotreatment stage a) of the method according tothe invention can also advantageously contain an element such asphosphorus and/or boron. This element can be introduced into the matrixor preferably deposited on the support. It is also possible to depositsilicon on the support, alone or with phosphorus and/or boron and/orfluorine.

The proportion by weight of oxide in said element is usuallyadvantageously less than 20%, preferably less than 10% and it is usuallyadvantageously at least 0.001%.

The metals of the catalysts used in hydrotreatment stage a) of themethod according to the invention are sulfur-containing metals ormetallic phases.

A preferred metallic catalyst used in hydrotreatment stage a) of themethod according to the invention comprises a nickel content rangingbetween 20% and 80% by weight, preferably between 55% and 65% by weight.The support of said catalyst is advantageously selected from the groupmade up of alumina, magnesium oxide and silica, and the supportpreferably consists of alumina.

A single catalyst or several different catalysts could be usedsimultaneously or successively in stage a) of the method according tothe invention without departing from the scope of the present invention.This stage can be carried out industrially in one or more reactors withone or more catalyst beds and preferably with a descending liquid flow.

The reaction exothermy during hydrotreatment is limited by any methodknown to the person skilled in the art: liquid product recycle,quenching by the recycle hydrogen, etc.

Stage b): Separation of at Least Part of the Water from the HydrotreatedEffluent from Stage a)

In stage b) of the method according to the invention, the hydrotreatedeffluent is subjected to a separation of at least part and preferablyall of the water, of at least one hydrocarbon-containing base, the waterbeing produced during hydrotreatment stage a).

The purpose of this stage is to separate the water from thehydrocarbon-containing effluent. What is referred to as water removal isthe elimination of the water produced by the hydrodeoxygenationreactions (HDO). More or less complete water removal advantageouslydepends on the water tolerance of the hydroisomerization catalyst usedin stage c) of the method according to the invention. Water removal canbe achieved by any means and techniques known to the person skilled inthe art, for example drying, passage through a desiccant, flash,decanting.

Stage c): Purification of the Effluent from Stage b)

In accordance with stage b) of the method according to the invention,said hydrocarbon-containing base from stage b) undergoes a stage ofelimination of the nitrogen compounds it contains.

The hydrocarbon-containing base from stage b) generally containsresidual organic nitrogen compounds that have not been removed duringhydrotreatment stage a) of the method according to the invention. It hasbeen observed that said residual organic nitrogen compounds arehydroisomerization catalyst inhibitors, they therefore have to beeliminated from said hydrocarbon-containing base prior tohydroisomerization stage d) of the method according to the invention.Removal of the residual organic nitrogen compounds can be achieved byany technique known to the person skilled in the art such as, forexample, the use of capture masses. What is referred to as capturemasses are aluminas, activated or not, silica-aluminas, zeolites,activated charcoal and ion-exchange resins. Stage c) of the methodaccording to the invention is preferably carried out over anion-exchange resin.

The effluents from stage c) are substantially nitrogen-free if notessentially completely nitrogen-free by conventional analyticalinstrumentation and they contain sulfur compounds such as H₂S. Thesulfur can come from a part of the feedstock from renewable sources usedin stage a), but it can also come from a sulfur compound deliberatelyadded in stage a) of the method in order to maintain the catalyst in thesulfurized state.

Thus, one advantage of the method is to use a combination of ahydrotreatment stage a) operating under precise operating conditionsallowing reduced hydrogen consumption and a hydroisomerization stageusing a particular hydroisomerization catalyst, without intermediategas-liquid separation, allowing both to treat a hydrotreated effluentcontaining sulfur compounds and to obtain a high diesel fuel base yield,as well as reduced H₂ consumption. The presence of sulfur compoundsrequires using a thioresistant hydroisomerization catalyst, i.e.tolerating the presence of sulfur compounds without degrading theproduced fuel yield, notably the diesel fuel base yield, and thequalities of this base.

Stage d): Hydroisomerization of the Hydrotreated Effluent from Stage c)

At least part of the liquid hydrocarbon-containing base obtained at theend of stage c) is hydroisomerized in the presence of a selectivehydroisomerization catalyst. The hydroisomerization catalysts used instage d) of the method according to the invention are advantageously ofbifunctional type, i.e. they have a hydro/dehydrogenizing function and ahydroisomerizing function.

In accordance with stage d) of the method according to the invention,the hydroisomerization catalyst comprises at least one group VIII metaland/or at least one group VIB metal as the hydrodehydrogenizing functionand at least one molecular sieve as the hydroisomerizing function.

According to the invention, the hydroisomerization catalyst compriseseither at least one noble metal of group VIII preferably selected fromamong platinum or palladium, active in their reduced form, or at leastone metal of group VIB, preferably selected from among molybdenum ortungsten, in combination with at least one non-noble metal of groupVIII, preferably selected from among nickel and cobalt, preferably usedin their sulfur-containing form.

In cases where the hydroisomerization catalyst comprises at least onegroup VIII noble metal, the total noble metal content of thehydroisomerization catalyst used in stage d) of the method according tothe invention advantageously ranges between 0.01 and 5% by weight inrelation to the finished catalyst, preferably between 0.1 and 4% byweight and more preferably between 0.2 and 2% by weight.

The hydroisomerization catalyst preferably comprises two group VIIInoble metals and it more preferably comprises platinum and palladium.

In cases where the hydroisomerization catalyst comprises at least onegroup VIB metal in combination with at least one group VIII non-noblemetal, the group VIB metal content of the hydroisomerization catalystused in stage c) of the method according to the invention advantageouslyranges, in oxide equivalent, between 5 and 40% by weight in relation tothe finished catalyst, preferably between 10 and 35% by weight and morepreferably between 15 and 30% by weight, and the group VIII metalcontent of said catalyst advantageously ranges, in oxide equivalent,between 0.5 and 10% by weight in relation to the finished catalyst,preferably between 1 and 8% by weight and more preferably between 1.5and 6% by weight.

The metallic hydro/dehydrogenizing function can advantageously beintroduced on said catalyst by any method known to the person skilled inthe art, such as, for example, comixing, dry impregnation, exchangeimpregnation.

In accordance with hydroisomerization stage d) of the method accordingto the invention, the hydroisomerization catalyst comprises at least onemolecular sieve, preferably at least one zeolite molecular sieve and,more preferably, at least one monodimensional 10 MR zeolite molecularsieve as the hydroisomerizing function.

Zeolite molecular sieves are defined in the “Atlas of Zeolite StructureTypes” classification, W. M. Meier, D. H. Olson and Ch. Baerlocher,5^(th) revised edition, 2001, Elsevier, which the present applicationalso refers to. The zeolites are classified according to their pore orchannel opening size.

Mono-dimensional 10 MR zeolite molecular sieves have pores or channelswhose opening is defined by a ring with 10 oxygen atoms (10 MR opening).The channels of the zeolite molecular sieve having a 10 MR opening areadvantageously non-interconnected monodimensional channels that directlyopen onto the outside of said zeolite. The monodimensional 10 MR zeolitemolecular sieves present in said hydroisomerization catalystadvantageously comprise silicon and at least one element T selected fromthe group made up of aluminium, iron, gallium, phosphorus and boron,preferably aluminium. The Si/Al ratios of the zeolites described aboveare advantageously those obtained upon synthesis or after post-synthesisdealumination treatments known to the person skilled in the art such as,without this list being exhaustive, hydrothermal treatments followed ornot by acid attacks, or direct acid attacks by mineral or organic acidsolutions. They are preferably, practically totally, in acidic form,i.e. the atomic ratio of the monovalent compensation cation (sodium forexample) to element T inserted in the crystal lattice of the solid isadvantageously below 0.1, preferably below 0.05 and more preferablybelow 0.01. Thus, the zeolites that go into said selectivehydroisomerization catalyst are advantageously calcined and exchanged byat least one treatment with a solution of at least one ammonium salt soas to obtain the ammonium form of the zeolites that, once calcined, leadto the acidic form of said zeolites.

Said monodimensional 10 MR zeolite molecular sieve of saidhydroisomerization catalyst is advantageously selected from among thezeolite molecular sieves of TON structural type, such as NU-10, EUO,selected from among EU-1 and ZSM-50, taken alone or in admixture, orzeolite molecular sieves ZSM-48, ZBM-30, IZM-1, COK-7, EU-2 and EU-11,alone or in admixture. Said monodimensional 10 MR zeolite molecularsieve is preferably selected from among the zeolite molecular sievesZSM-48, ZBM-30, IZM-1 and COK-7, alone or in admixture. More preferably,said monodimensional 10 MR zeolite molecular sieve is selected fromamong the zeolite molecular sieves ZSM-48 and ZBM-30, alone or inadmixture.

Most preferably, said monodimensional 10 MR zeolite molecular sieve isZBM-30 and more preferably yet, said monodimensional 10 MR zeolitemolecular sieve is ZBM-30 synthesized with the triethylene tetramineorganic structurant.

Zeolite ZBM-30 is described in patent EP-A-46,504, and zeolite COK-7 isdescribed in patent applications EP-1,702,888 A1 or FR-2,882,744 A1.

Zeolite IZM-1 is described in patent application FR-A-2,911,866.

TON structural type zeolites are described in the book “Atlas of ZeoliteStructure Types”, W. M. Meier, D. H. Olson and Ch. Baerlocher, 5^(th)revised edition, 2001, Elsevier.

The TON structural zeolite is described in the aforementioned book“Atlas of Zeolite Structure Types” and the NU-10 zeolite in patentsEP-65,400 and EP-77,624.

The proportion of monodimensional 10 MR zeolite molecular sieveadvantageously ranges between 5 and 95% by weight, preferably between 10and 90% by weight, more preferably between 15 and 85% by weight and mostpreferably between 20 and 80% by weight in relation to the finishedcatalyst.

Said hydroisomerization catalyst preferably also comprises a binderconsisting of a porous mineral matrix. Said binder can advantageously beused during the stage of forming said hydroisomerization catalyst.

Forming is preferably performed with a binder consisting of a matrixcontaining alumina, in any form known to the person skilled in the art,and more preferably with a matrix containing gamma alumina.

The hydroisomerization catalysts obtained are formed as grains ofvarious shapes and dimensions. They are generally used in form ofcylindrical or polylobed, bilobed, trilobed extrudates of straight ortwisted shape, but they can possibly be manufactured and used in form ofcrushed powders, bars, rings, balls, wheels. Other techniques thanextrusion, such as pelletizing or drageification, can be advantageouslyused.

In cases where the hydroisomerization catalyst contains at least onenoble metal, the noble metal contained in said hydroisomerizationcatalyst has to be advantageously reduced. One preferred method forconducting metal reduction is treatment under hydrogen at a temperatureranging between 150° C. and 650° C. and at a total pressure rangingbetween 1 and 250 bars. For example, reduction consists in a 2-hour stepat 150° C., then a temperature rise up to 450° C. at a rate of 1°C./min, then again a 2-hour step at 450° C.; throughout this reductionphase, the hydrogen flow rate is 1000 normal m³ hydrogen/m³ catalyst andthe total pressure is maintained constant at 1 bar. Any ex-situreduction method can advantageously be considered.

In accordance with stage d) of the method according to the invention, inthe hydroisomerization zone, the feedstock is contacted, in the presenceof hydrogen, with said hydroisomerization catalyst, at operatingtemperatures and pressures advantageously allowing non-convertinghydroisomerization of the feedstock. This means that hydroisomerizationis carried out with a conversion of the 150° C.+ fraction to a 150° C.−fraction below 20% by weight, preferably below 10% by weight and morepreferably below 5% by weight.

Thus, hydroisomerization stage d) of the method according to theinvention operates at a temperature ranging between 150° C. and 500° C.,preferably between 150° C. and 450° C. and more preferably between 200°C. and 450° C., at a pressure ranging between 1 MPa and 10 MPa,preferably between 2 MPa and 10 MPa and more preferably between 1 MPaand 9 MPa, at an hourly space velocity advantageously ranging between0.1 h⁻¹ and 10 h⁻¹ preferably between 0.2 h⁻¹ and 7 h⁻¹ and morepreferably between 0.5 h⁻¹ and 5 h⁻¹, at a hydrogen flow rate such thatthe hydrogen/hydrocarbon volume ratio advantageously ranges between 70and 1000 Nm³/m³ feedstock, preferably between 100 and 1000 Nm³hydrogen/m³ feedstock and more preferably between 150 and 1000 Nm³hydrogen/m³ feedstock.

The possible hydroisomerization stage is preferably operated with aconcurrent flow.

Stage e): Separation, from the Effluent from Stage d), of the Hydrogen,the Gases and at Least One Diesel Fuel Base

In accordance with the method according to the invention, in stage d) ofthe method according to the invention, the hydroisomerized effluent issubjected at least partly, preferably totally, to one or moreseparations. The purpose of this stage is to separate the gases from theliquid and notably to recover the hydrogen-rich gases that can alsocontain lights such as the C₁-C₄ cut and at least one diesel fuel cutand a naphtha cut. Upgrading of the naphtha cut is not the object of thepresent invention, but this cut can be advantageously sent to a steamcracking or catalytic reforming plant.

Gas Treatment and Recycle

The gas containing the hydrogen that has been separated in stage e) is,if necessary, at least partly treated in order to reduce its proportionof lights (C₁ to C₄).

It is possible to add to the recycle gas of stage e) a certain amount ofsulfur compound (such as DMDS, dimethyl disulfide) that produceshydrogen sulfide H₂S through thermal decomposition. This device allowsto maintain, if necessary, the hydrotreatment catalyst and/or thehydroisomerization catalyst in the sulfurized state. Advantageously, theamount of sulfur compound introduced is such that the H₂S content of therecycle gas is at least 15 ppm vol, preferably at least 0.1% vol, oreven at least 0.2% vol.

The recycle hydrogen can be advantageously introduced with the inflowingfeedstock in stage a) and/or in stage d) and/or in form of quenchhydrogen between the hydrotreatment and/or hydroisomerization catalystbeds.

Products Obtained

The product provided by this method exhibits excellent characteristicsand it therefore is a diesel fuel base of excellent quality:

-   -   its sulfur content is below 10 ppm weight    -   its total aromatics content is below 5% by weight, and its        polyaromatics content below 2% by weight    -   the cetane number is excellent, above 55    -   the density is below 840 kg/m³ and in most cases below 820 kg/m³    -   the kinematic viscosity at 40° C. ranges from 2 to 8 mm²/s    -   its cold strength properties are compatible with the current        standards, with a cold filter-plugging point below −15° C. and a        cloud point below −5° C.

BRIEF DESCRIPTION OF DRAWING

The invention also relates to a plant schematically shown in FIG. 1,that can be used for implementing the method according to the invention.

As shown in FIG. 1, the feedstock from renewable sources is fed throughline (1) into hydrotreatment zone (3) operating in the presence ofhydrogen, the hydrogen being delivered through pipe (2). Inhydrotreatment zone (3), the feedstock is contacted with ahydrotreatment catalyst described above. The hydrotreated effluent isthen fed into a decantation zone (4) so as to separate the water fromthe hydrocarbon-containing compounds. The hydrocarbon fraction isrecovered and sent to a purification stage (5) allowing to remove theorganic nitrogen compounds. The effluents thus purified are sent to ahydroisomerization stage (7) using the zeolite type selectivehydroisomerization catalyst, through line (6). According to FIG. 1, theliquid diesel fuel base fraction is fed, with a hydrogen stream throughline (6), into hydroisomerization zone (7) containing the selectivehydroisomerization catalyst described above. The effluent thushydroisomerized is then sent via pipe (8) to separation zone (9) so asto separate the gases from at least one diesel.

EXAMPLE 1

Stage a): Hydrotreatment

In a reactor whose temperature is controlled so as to provide isothermaloperation and equipped with a fixed bed laden with 190 ml hydrotreatmentcatalyst based on nickel and molybdenum, having a nickel oxide contentequal to 3% by weight, a molybdenum oxide content equal to 16% by weightand a P₂O₅ content equal to 6%, the catalyst having been previouslysulfurized, 170 g/h prerefined rape oil of density 920 kg/m³, having asulfur content below 10 ppm weight, of cetane number 35, and whosecomposition is given hereafter is introduced:

Fatty acid glycerides Fatty chain nature % by mass Palmitic C16:0 4Palmitoleic C16:1 <0.5 Stearic C18:0 2 Oleic C18:1 61 Linoleic C18:2 20Linoleic C18:3 9 Arachidic C20:0 <0.5 Gadoleic C20:1 1 Behenic C22:0<0.5 Erucic C22:1 <1

700 Nm³ hydrogen/m³ feedstock are fed into the reactor maintained at atemperature of 300° C. and at a pressure of 5 MPa.

Stage b): Separation of the Water from the Effluent from Stage a)

All of the hydrotreated effluent from stage a) is subjected to adecantation stage so as to remove the water produced during thehydrotreatment stage.

Stage c): Purification of the Effluent from Stage b) Over a Capture Mass

All of the hydrotreated and decanted effluent from stage b) is sent to afixed-bed reactor containing an Amberlyst 35Dry ion-exchange resinmanufactured by the Amberlyst Company under the following operatingconditions:

-   -   feedstock flow rate: 150 g/h    -   mass of Amberlyst 35Dry: 100 g    -   operating pressure: 50 bars    -   temperature: 100° C.

Stage d): Hydroisomerization of the Hydrotreated Effluent from Stage c)Over a Catalyst According to the Invention

1) Preparation of the Hydroisomerization Catalyst C1

The hydroisomerization catalyst is a catalyst containing a noble metaland a ZBM-30 monodimensional 10 MR zeolite. This catalyst is obtainedaccording to the operating method described hereafter. The ZBM-30zeolite is synthesized according to the BASF patent EP-A-46,504 with thetriethylene tetramine organic structurant. The crude synthesis ZBM-30zeolite is subjected to calcination at 550° C. in a dry air stream for12 hours. The H-ZBM-30 zeolite (acid form) thus obtained has a Si/Alratio of 45. The zeolite is mixed with a SB3 type alumina gel providedby the Condéa-Sasol Company. The mixed paste is then extruded through a1.4 mm-diameter die. The extrudates thus obtained are calcined at 500°C. for 2 hours in an air stream. The proportion by weight of H-ZBM-30 is20% by weight. The support extrudates are thereafter subjected to astage of dry impregnation by an aqueous solution of platinum saltPt(NH₃)₄Cl₂ and Pd(NH₃)₄Cl₂, left to mature in a water maturator for 24hours at ambient temperature, then calcined for two hours in a dry airstream in a traversed bed at 500° C. (temperature rise step 5° C./min).The proportions by weight of platinum and palladium in the finishedcatalyst after calcination are 0.80% and 0.29% respectively.

2) Hydroisomerization of the Hydrotreated Effluent from Stage c)

The effluent is hydroisomerized in a waste hydrogen stream over catalystC1 in a hydroisomerization reactor under the following operatingconditions:

-   -   hourly space velocity (volume of feedstock/volume of        catalyst/hour)=1.5 h⁻¹    -   total operating pressure: 50 bars    -   hydrogen/feedstock ratio: 1000 normal litres/litre.

The temperature is adjusted so as to have a conversion of the 150° C.+fraction to a 150° C.− fraction below 10% by weight uponhydroisomerization. Before testing, the catalyst undergoes a reductionstage under the following operating conditions:

-   -   hydrogen flow rate: 1600 normal litres per hour and per litre        catalyst    -   ambient temperature rise 120° C.: 10° C./min    -   one-hour step at 120° C.    -   temperature rise from 120° C. to 450° C. at 5° C./min    -   two-hour step at 450° C.    -   pressure: 1 bar.

The hydroisomerized effluent is then characterized. The yields and thefuel properties are given in Table 1 hereafter.

TABLE 1 Product characteristics (T = 350° C., P = 50 bar, H₂/HC = 1000NL/L) 150° C.⁻ cut  8% by weight 150° C.⁺ cut (Diesel) 92% by weightCetane number (ASTMD613) 62 Cold filter-plugging point (° C.) −31

The method according to the invention thus allows to obtain diesel fuelbases with a good yield and of excellent quality corresponding to thecurrent specifications.

COMPARATIVE EXAMPLE

A feedstock identical to the feed of Example 1 is used in a processcomprising a hydrotreatment stage a) operating under the same operatingconditions and with the same catalyst as in stage a) of Example 1. Thesame water separation b) and nitrogen compound removal c) stages as inExample 1 and under the same conditions are carried out so as to recovera liquid hydrocarbon-containing base that is subsequently subjected to ahydroisomerization stage d) operating under the same operatingconditions as stage c) of Example 1, but with a differenthydroisomerization catalyst.

The hydroisomerization catalyst is a catalyst containing a noble metaland a ZSM-22 monodimensional 10 MR zeolite. This catalyst is obtainedaccording to the operating method described hereafter. The ZSM-22zeolite is synthesized according to the method described by Ernst. Etal. (Applied Catalysis, 1989, 48, 137): 72 grams silica sol (Ludox AS40,DuPont) are diluted in 124 ml water; another solution containing 3.54grams Al₂(SO₄)₃, 18H₂O, 7.75 grams KOH and 16.7 grams diaminohexane in177 ml water is added to the first solution and stirred. The gelobtained is then placed in stainless steel autoclaves at 50° C. Aftertwo-day synthesis, the autoclaves are opened and the synthesized zeoliteis washed with water and filtered. The Si/Al atomic ratio of thecrystallized structure is 30. The solid is thereafter thermally treatedin a nitrogen stream (10 ml N2/minute/gram of solid) for 5 hours at 400°C., then for 16 hours at 550° C. in an oxygen stream (10 mlO₂/minute/gram of solid). In order to exchange the alkaline cations withthe ammonium ions, the solid is then brought to reflux for 4 hours in anaqueous solution of ammonium chloride (100 ml solution/gram of solid;ammonium chloride concentration 0.5 M). The sample is finally washedwith distilled water to remove the alkaline chloride (silver nitratetest negative), then it is dried for one night in a drier at 60° C. Thezeolite is thereafter mixed with a SB3 type alumina gel provided by theCondéa-Sasol Company. The mixed paste is subsequently extruded through a1.4 mm-diameter die. The extrudates thus obtained are calcined at 500°C. for 2 hours in an air stream. The proportion by weight of H-ZSM-22 is14% by weight. The support extrudates are thereafter subjected to astage of dry impregnation by an aqueous solution of Pt(NH₃)₄Cl₂ andPd(NH₃)₄Cl₂, left to mature in a water maturator for 24 hours at ambienttemperature, then calcined for two hours in a dry air stream in atraversed bed at 500° C. (temperature rise step 5° C./min). Theproportions by weight of platinum and palladium in the finished catalystafter calcination are 0.58% and 0.21% respectively.

The catalyst reduction stage is the same as the stage carried out forhydroisomerization catalyst C1, as well as the operating conditions ofthe hydroisomerization test. The temperature is adjusted so as to haveproduct qualities comparable to those obtained with catalyst C1.

The hydroisomerized effluent is subsequently characterized. The yieldsand the fuel properties are given in Table 2.

TABLE 2 Product characteristics 150° C.⁻ cut (% by weight) 12 150° C.⁺cut (Diesel, % by weight) 88 Product quality of the 150° C.⁺ cut Cetanenumber (ASTMD613) 63 Cold filter-plugging point (° C.) −28 Sulfurcontent (ppm by weight) <10

In relation to hydroisomerization catalyst C1, it can be seen that usingthe ZSM-22 based hydroisomerization catalyst leads to a more significantlight products loss for comparable product qualities.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The preceding preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

In the foregoing and in the examples, all temperatures are set forthuncorrected in degrees Celsius and, all parts and percentages are byweight, unless otherwise indicated.

The entire disclosures of all applications, patents and publications,cited herein and of corresponding French application No. 08/03.531,filed Jun. 24, 2008, are incorporated by reference herein.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. A method of treating a feedstock from a renewable source, comprisingthe following stages: a) hydrotreatment of said feedstock from arenewable source in the presence of a fixed-bed catalyst, said catalystcomprising a hydro-dehydrogenizing function and an amorphous support, ata temperature ranging between 200° C. and 450° C., at a pressure rangingbetween 1 MPa and 10 MPa, at an hourly space velocity ranging between0.1 h⁻¹ and 10 h⁻¹ and in the presence of a total amount of hydrogenmixed with the feedstock such that the hydrogen/feedstock ratio rangesbetween 150 and 750 Nm³ hydrogen/m³ feedstock, b) separation, from theeffluent from stage a), of at least part of resultant water and at leastone hydrocarbon-containing base, c) removal of the nitrogen compoundsfrom said hydrocarbon-containing base from stage b), d)hydroisomerization of at least part of said hydrocarbon-containing basefrom stage c) in the presence of a fixed-bed hydroisomerizationselective catalyst, said catalyst comprising at least one group VIIImetal and/or at least one VIB group metal and a monodimensional 10 MRzeolite molecular sieve that is ZSM-48 or ZBM-30, alone or in admixture,said stage c) being carried out at a temperature ranging between 150° C.and 500° C., at a pressure ranging between 1 MPa and 10 MPa, at anhourly space velocity ranging between 0.1 h⁻¹ and 10 h⁻¹ and in thepresence of a total amount of hydrogen mixed with the feedstock suchthat the hydrogen/feedstock ratio ranges between 70 and 1000 Nm³/m³feedstock, e) separation, from the effluent from stage d), of thehydrogen, other gases and at least one diesel fuel base.
 2. A method asclaimed in claim 1, wherein stage a) operates in the presence of a totalamount of hydrogen mixed with the feedstock such that thehydrogen/feedstock ratio ranges between 150 and 650 Nm³ hydrogen/m³feedstock.
 3. A method as claimed in claim 2, wherein stage a) operatesin the presence of a total amount of hydrogen mixed with the feedstocksuch that the hydrogen/feedstock ratio ranges between 150 and 600 Nm³hydrogen/m³ feedstock.
 4. A method as claimed in claim 1, wherein stagec) is carried out over an ion-exchange resin.
 5. A method as claimed inclaim 1, wherein said monodimensional 10 MR zeolite molecular sieve isZBM-30.
 6. A method as claimed in claim 5, wherein said monodimensional10 MR zeolite molecular sieve is ZBM-30 synthesized with triethylenetetramine organic structurant.
 7. A method as claimed in claim 1,wherein said hydroisomerization catalyst comprises either at least onenoble metal of group VIII or at least one metal of group VIB, incombination with at least one non-noble metal of group VIII.
 8. A methodas claimed in claim 1, wherein said hydroisomerization catalystcomprises platinum and palladium.
 9. A method as claimed in claim 1,wherein the feedstock comprises at least one vegetable oil or animalfat, essentially containing triglycerides and fatty acids or esters,with hydrocarbon fatty chains having a number of carbon atoms rangingbetween 6 and
 25. 10. A method according to claim 9, wherein thefeedstock comprises any palm, palm-nut, copra, castor and cotton oil,peanut, linseed, crambe and jatropha oil, all the oils resulting fromsunflower or rapeseed through genetic modification or hybridization, aswell as algae oils, waste kitchen oils or animal oils.